1. Field of Invention
The present invention relates to a flat lock.
2. Related Prior Art
Conventional flat locks each have a cylinder mounted in a door or the like, a tumbler co-axially pivotably mounted in the cylinder and a latch co-axially pivotably mounted on the tumbler. The cylinder has an inner surface on which a number of separate longitudinal ribs are formed. The tumbler has a number of slots transversely formed therein. The slots each communicate with a relatively wide cylindrical recess at a terminal portion thereof. Four springs are respectively received in the cylindrical recesses. Four strips each have a first tip, a second tip, a relatively small ear transversely formed thereon and a slot longitudinally formed therein. The strips are received respectively in the slots defined in the tumbler. When the strips are respectively received in the slots formed in the tumbler, the ears protruding therefrom are sited against the springs so that the first tips of the strips are biased out of the tumbler by means of the springs. The first tips of the strips are trapped between two adjacent ribs formed on the inner surface of the cylinder so that the tumbler, together with the latch, is restrained from pivoting relative to the cylinder. The slots formed in the strips align with one another when the strips are mounted in slots formed in the tumbler so that a key is insertable therethrough. The slots formed in the strips differ from one another in length so that the first tips of the strips are urged into the tumbler when the key is inserted through the slots defined in the strips, i.e., the first tips of the strips are not trapped between two adjacent ribs formed on the inner surface of the cylinder. Thus, the tumbler is permitted to pivot with respect to the cylinder. Thus, the latch is permitted to pivot relative to the cylinder. But, the flat locks can be easily picked by inserting a slender element through the slots defined in the strips and pressing strips toward the second tips thereof so that the first tips thereof are moved into the tumbler. Therefore, the present invention is intended to solve the above-mentioned problem.